Simple answer is that some movies are "near" impossible to copy, NEAR impossible !(they can be copied) one must remember it's illegal to copy any of em without exception, but whos looking, and with good new DVD's costing only $6 - $10 why bother stuffing around.
OK now I have backed up my dvd collection with 1 click and dvd43, of my 400+ collection (and that only includes movies I give at least 8.5+/10, the rest are put away, only 4 ever refused to copy at first the simple way, Green Mile, Titanic, Die Hard, and Dances with wolves, but having the originals it really is no big drama.
I'm probably fussy but some movies I have played at least 30 times are still as they were bought, brand new, not a mark or scratch or fingerprint in sight, it's not hard to keep em like that, from the case to the player and from the player to it's case with no stops via the coffee table or other place.
I recently upgraded to a new 1000 w all region Sony system and found the 8x Ritek copies that played up on a good LG all region home theatre now worked fine.
There are several decrypters and like most things you get what you pay for, 1 click is a damm good program with a simplicity a 5 year old can follow, dvd43 works fine for 99% so why stress about the odd disk that wil not copy.
The asian copies are fairly easy to see and have no encryption (the first sign of a fake), BUT the US and UK fakes are real good, ignore the sealed case, the cellophane seals are easy to buy, that alone means the new and sealed DVD you just bought has allready been copied, live with it, with a good Taiyo Yuden Master disk costing < $1 and Amaray case 50c, the burner $60 or so, you may see why everyone is doing it, nevermind the DVD popular player/HDD recorders
You can't go wrong with 1 Click and DVD43 but make sure you have the latest version of both.